Why Curing Agents Are a Necessity When Laying Self-Compacting Concrete

Posted on: 28th September 2020

Curing agent being sprayed over concrete
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Last updated: June 2026

Self-compacting concrete AKA Self-consolidating concrete (SCC) is a well-established product in the industry and is trusted in some of the world’s highest-profile and advanced construction projects.

Unlike conventional concrete, self-compacting concrete is a semi-liquid that pours and flows quickly and levels naturally under its own weight, with very little manual labour. It does still need guiding during the pour and dappling afterwards, though.

Ideal for foundations and underground structures, self-compacting concrete is easy to pour into the required area, without the need for vibrators or mechanical compaction. After pouring, chemicals are sprayed on to the mix to create a strong, durable concrete floor. These are called concrete curing agents.

Quick Answer: When self-compacting concrete is poured, the water near the surface can evaporate faster than the water deeper in the slab. If that happens, the surface dries before the rest of the slab, which leads to cracking, dusting, and a floor that cannot carry load as well as it should. A curing agent sprayed onto the fresh concrete forms a membrane that slows this surface evaporation and allows the slab to cure more evenly throughout. Water-based curing agents work over 7 days and are non-flammable; solvent-based versions work over 28 days and are flammable, so need more care during application.

Why should I use concrete curing agents?

When concrete cures, water within the concrete evaporates. If water near the surface of a concrete slab evaporates too quickly, the concrete dries at the surface before drying further down the slab.  This causes several problems, most notably:

  • A surface that’s prone to cracking and dusting (where the surface scratches away to powder).
  • A slab that won’t be able to bear heavy weights as easily, because it has lower strength at the surface.

A concrete curing agent forms a membrane over the top of the concrete slab while it cures.  This stops the water near the surface of the slab evaporating too quickly and hence helps to reduce cracking and dusting.

When a slab has uniform strength, it means it can bear weight and withstand challenging environments more easily – so, curing helps a concrete floor perform to its full potential.

What are the options?

There are two types of concrete curing agents – water-based and solvent-based. In terms of performance, these are similar. The differences occur during application.

  • Solvent-based – this is sprayed on as an a clear liquid and works over a longer time period – 28 days. Because it is solvent-based, it is flammable and should be handled and applied with care.
  • Water-based – this goes on as a white liquid which dries clear. It works over 7 days and penetrates the surface to prevent cracking. Water-based curing agents are ideal for projects where there is fast turnaround time.  It is also suitable for use on self-compacting concrete floors.  Being water-based, there are minimal handling concerns, as the product is non-flammable and non-toxic.

The Metex range of high-quality Chapin sprayers come with FKM seals and gaskets. These concrete sprayers, like the Chapin 1949, are used by groundworkers when applying curing agents to free-flowing self-compacting concrete and may be used for the application of concrete mould release agents.

The range is made up of heavy-duty steel sprayers, commercial plastic sprayers and industrial backpack sprayers.

View our range of Metex Chemical Sprayers here – and please feel free to get in touch if you need advice on curing agent sprayers – we’re happy to help.

Frequently Asked Questions

A concrete curing agent is a liquid compound sprayed onto the surface of fresh concrete immediately after it has been poured and finished. It forms a thin membrane over the slab that slows the rate at which surface moisture evaporates, allowing the concrete to cure more evenly from top to bottom. Without it, the surface dries faster than the concrete beneath, which leads to a weaker, more brittle top layer that is prone to cracking and dusting.

SCC has a higher water content and flows further than traditional concrete, which means the surface area exposed to evaporation is larger and the risk of differential drying is greater. Because SCC is also used in applications where a high-quality, load-bearing surface finish is required, like industrial floors, any surface weakness from poor curing is more likely to cause problems in use. Applying a curing agent immediately after the pour is the most reliable way to protect the surface during the critical early hours of the curing process.

Water-based curing agents go on as a white liquid that dries clear and work over a 7 day curing period. They are non-flammable and non-toxic, which makes them straightforward to handle and apply on site. Solvent-based curing agents are applied as a clear liquid, work over a longer 28 day period, and are flammable, so require more care during storage and application. In terms of curing performance the two are broadly comparable; the choice usually comes down to the specific project requirements and site conditions.

A curing agent should be applied as soon as the concrete surface has been finished and any surface bleed water has evaporated, but before the surface has had a chance to dry out. In warm or windy conditions this window can be short, so it is important to have the sprayer ready before the pour is complete rather than preparing it afterwards. Applying the curing agent too late reduces its effectiveness, as the surface membrane it needs to form will not bond properly to a partially dried surface.

A pressurised chemical sprayer with seals and gaskets compatible with the curing agent being used is essential. Standard garden sprayers are not suitable as the chemicals in curing agents, particularly solvent-based products, will degrade standard rubber seals quickly. Metex supply the Chapin range of industrial sprayers fitted with FKM seals and gaskets, which are resistant to the chemicals used in both water-based and solvent-based curing agents and are used by groundworkers specifically for this application.

Light foot traffic is generally possible within 24 hours of pouring, but the concrete will not reach its full design strength for several weeks. During the curing period it is important not to subject the slab to heavy loads or impact, and to keep it protected from rapid temperature changes and direct sunlight where possible. The curing agent plays an important role during this period by maintaining the surface moisture balance while the concrete continues to gain strength beneath.

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